The stacking of antiaromatic compounds has not been well investigated. Theoretical calculations have proposed that staking of two antiaromatic systems lead to three-dimensional aromaticity, which results from mutual interactions between frontier orbitals of each π-system. However, there has been no experimental support for this interesting prediction.

Norcorrole is a ring-contracted porphyrin, which shows distinct antiaromatic character. We have discovered that diphenylnorcorrole Ni(II) adopts a triple-decker π–π stacked structure in the solid state. A significant reduction of antiaromaticity of the norcorrole skeleton was observed.